The present invention generally relates to high-speed data communications. More specifically, the invention relates to a system and method for line characterization within a digital subscriber line (DSL) system using time-domain reflectometry (TDR).
Line characterization remains a problem in digital subscriber line (DSL) systems, and especially in asymmetrical DSL (ADSL) systems. Typically, phone companies rely on automated test equipment for line characterization at low frequencies. Upon request from a management system, the transmission line is disconnected from the line termination equipment, and a test bus is coupled to the transmission line. This test bus is serviced by centralized test equipment, which tests the integrity of the line. The test equipment typically measures the direct current (DC) resistance of the loop with its terminating set of phones rather than measuring alternating current (AC) resistance. Although the DC resistance provides information about the loop length, it may not identify other impairments that affect the performance of the DSL, which typically operates at a predetermined frequency range. Furthermore, disconnection of the transmission line and the insertion of a test bus may produce disturbance effects and further influence the measurement of line characteristics.
Therefore, there is a need in the industry for a system and method of characterizing transmission lines without using test equipment that may introduce disturbance effects. Moreover, in the context of DSL and ADSL systems, there is a need for a system and method of characterizing transmission lines at frequencies used in DSL in order to identify impairments that may not be detectable from DC resistance measurements.
The present disclosure relates to a system and method for characterizing transmission lines used in digital subscriber line (DSL) systems. The system can be broadly conceptualized as a DSL system in which the DSL system components are configured to analyze the characteristics of a transmission line using time domain reflectometry (TDR).
Briefly described, a transmitter transmits a predetermined test signal from a point of origin to a DSL transmission line. The transmission line reflects a portion of the signal back to the point of origin where a receiver receives the reflected signal. This reflected signal is analyzed to determine transmission line characteristics.
In architecture, the system comprises a transmitter configured to transmit the predetermined test signal, a receiver configured to receive the reflected signal, and an analyzer configured to determine transmission line characteristics as a function of the received signal and the transmitted signal.